fungus, mildew

I planted Brown Eyed Susan's too close together and they got mildew, really badly. I cut them back to about 3 inches but even those short stems are white.....how about next year? Will my soil be affected......I tried the milk/water treatment but think they might be beyond that...don't like chemicals....PS This is in my raised bed veg garden......they looked great but what a mistake...Help !!!!! Worried. Will it be safe to plant something in the same spot in 2015? AnnFran

Do you know what type of mildew? Powdery Mildew is very common, so I have sort of focused on that, but there are others that are similar.

Powdery Mildew is all over the place, not so much soil borne. You cannot avoid it.
I would remove every other one, so they are better spread out. They ought to be fine next year. Powdery Mildew does not really affect the plant inside, much. I would do a clean up spray now to kill whatever spores might try to over winter.
Plant something smaller in between, if there is room, or just a thick mulch.

Milk is a sort of spotty treatment, sometimes it seems to work, other times not.
Baking soda is supposed to help, but add carbonate and sodium to the soil. This is not much of a problem if you are on an acidic soil, but it can build up and cause problems if you treat with it too often.
Safest treatment is one of the chemical fungicides that breaks down in the sun and wind. Short lived, but not lingering in the environment.

Non-chemical approach-
1) Select plants, and varieties of plants, that are resistant to the local pests and diseases.
2) Plant them at the recommended spacing for good air flow between the plants.
3) Mixed planting, so a pest or disease does not have a lot of plants to build up to excessive populations.
4) For pests, cultivate flowers that will feed them in between pest population rising and falling. Many predatory insects will also eat pollen, some will eat nectar. Select small, open flowers in clusters that are easy for them to get to. Achillea is an example.
5) Plant the plants in the right area, sun/shade, and good drainage, and so on so they are as healthy as can be without forcing too much new tender growth all at once. Plants that grow a bit more slowly seem to have tougher leaves that do not get so many diseases.

I agree with Diana, also there are some types of these plants that will grow anywhere without a bit of mould, insect problems and can take drought like no other plants, and this also applies to a lot of different plant type too, BUT, there are some of the same family that no matter where, how or what, they are prone to virus, mould, Insect troubles or any other stuff nature throws at them. I have huge problems with this mould when trying to grow Hollyhocks, the first year, no problem, second year and awaiting the flowers to appear, the whole plants from top to bottom get covered in grey mould and there is NO holding it back.

All I can suggest you try is, as soon as you see a tiny blotch of this on the leaf, remove these leaves, Some folks say it works but it hasn't for me, Hollyhocks are re-known for this BUT Not sure about your Brown Eyed Susan.

Someone else suggested a very weak mix of water and vinegar BUT I have not tried that yet.

Thank you for helping me with the powdery mildew problem...... will however, if I plant something in the same spot next year, can I expect mildew? I now have it on squash...... I wonder will it winter over in the soil.....Zone 5. Thanks for your opinions, I value them.

If you plant something that tends to get powdery mildew, then it will get powdery mildew. Not because the fungus overwintered, or came from the plants you are growing now, but because that is a spot where powdery mildew can thrive.
To avoid powdery mildew plant something that does not get it.

Diana is right, Powdery Mildew and Grey Mould will grow freely on some plants YET there could be a dozen other different plants growing side by side AND the others don't take the mildew or mould.
I find BUT, most plants that have small hairs on their stems or foliage, example, Tomato's Cucumbers, many other flowering plants like Hollyhocks etc, BUT as mentioned by Diana, these problems don't live or stay dormant within the soil, they are usually air born, or spread by our insects travelling from one plant to the next, that's why I normally cut off the affected foliage to help prevent the spread BUT not always preventative.
It's a case of trying to remember IF you had it one years, you more than likely will find another attack on the same plants the following year IF growing in the same area.
Lack of air flow around the plants helps these problems get hold and also try to water the soil around the roots and try NOT water the foliage as this can prevent the mould or Mildew.

Hope you can get this sorted out soon BUT I can tell you, these diseases dont kill the plants normally.

The different fungi we call mildew (powdery mildew, downy mildew and others) each thrive in different conditions: temperature, humidity and so on.
If the conditions are right in a particular spot in the garden, then any susceptible plant planted there is highly likely to get mildew.
If the conditions are wrong for a certain mildew in a particular area, then even a susceptible plant is not as likely to get it, or at least would get much less of whatever mildew we are talking about.